As the basis of deterministic delivery of Time-Triggered Ethernet(TTE), the accurate clock synchronization is influenced by synchronization mechanism, clock drift and receive window. A model of node and switch supporting synchronization service was designed to transmit multi-class messages. The time determinability of TTE was studied by theoretical analysis and computer simulation, which verified that TTE could be a deterministic network. Through the study of the effect of clock synchronization accuracy on time triggered communication, the synchronization cycle boundary and receive window boundary of TT message loss event were find, which forms a basis for TTE synchronization parameter settings.